Ha, Song Son

A new FPGA-based approach for a data diode transmitting data unidirectionally from a high security zone to a lower security zone is evaluated and implemented. With the FPGA implementation, the need of additional hardware could be minimized compared to most state-of-the-art data diode realizations. The proposed data diode is designed to use the available backplane bus communication protocol between the programmable logic controller (PLC) and its connected peripherals. To demonstrate the universal approach an open-source platform based on the Revolution Pi (RevPi) and its backplane bus is used. Principally the data diode behaves as a mirror presenting the complete protected system behind the high security zone including the RevPi controller and its devices to the information technology (IT) network. Another controller within the lower security zone is used to imitate the operational technology (OT) process. Our approach is not limited to the above controller and can be applied to any type of PLC. The only requirement is that the communication protocol on the backplane bus is known and can be modified for this purpose.

In the context of Industry 4.0 and the Industrial Internet of Things, an exponential increase in the interconnection of machines and smart devices can be observed together with an increase of interconnections between Operation Technology (OT) and Information Technology (IT) networks as well as Cloud systems. This development is linked to the user's expectation for suitable security solutions, where it remains a challenging task to ensure that, e.g. a specific Safety Integrity Level (SIL) level can be maintained in view of possible potential cyberattacks. In this case, a data diode can be a suitable solution. In this paper a data diode prototype is presented being integrated into an industrial network analyzing the communication on the backplane bus of an Open Source Industrial PC called Revolution Pi. The advantage of our approach is that the data diode is totally transparent from the IT to the OT network, because all process data behind the data diode are mirrored into the IT network within a few system cycles. The security and reliability issues related with this approach are also discussed and evaluated.